Occupational exposure to secondhand cannabis smoke along law enforcement officers prividing security at outdoor concert events



Numerous states within the USA have legalized cannabis for medical or non-medical (adult/recreational) use. With the increased availability and use of cannabis, occupational and environmental exposures to secondhand cannabis smoke (SHCS) raise concerns over whether non-users may be at risk for a ‘contact high’, impaired neurocognitive function, harm from irritants and carcinogens in smoke, or potentially failing a cannabis screening test. The extent of health effects from potential occupational exposure to SHCS is unknown. This is a study of occupational exposures to SHCS among law enforcement officers (LEOs) providing security at outdoor concerts on a college campus in a state where adult use of cannabis is legal.


Investigators evaluated a convenience sample of LEOs’ potential exposure to SHCS and symptoms experienced while providing security during two open-air stadium rock-n-roll concerts on consecutive days in July 2018. During each event, full-shift area and LEO personal air samples were collected for ?9-tetrahydrocannabinol (?9-THC), the psychoactive component of cannabis. Urine (pre- and postevent; n = 58) and blood (postevent; n = 29) were also collected and analyzed for ?9-THC and two of its metabolites [11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) and 11-nor-hydroxy-delta-9-tetrahydrocannabinol (OH-THC)]. Urine samples were analyzed using ultrahigh performance liquid chromatography coupled with positive electrospray ionization tandem mass spectrometry and results were compared with the Department of Transportation guidelines for urine screening for cannabis. Blood (postevent) samples were also collected and the plasma fraction was tested for ?9-THC, THC-COOH, and OH-THC using high-performance liquid chromatography coupled with mass spectrometry. LEOs also completed a medical questionnaire asking about symptoms experienced during the concerts.


Twenty-nine LEOs participated in the evaluation. Measurable amounts of ?9-THC were found in area (concentrations ranged from non-detectable to 330 ng m-3) and personal air samples (53-480 ng m-3). Small amounts (<1.0 ng ml-1) of a ?9-THC metabolite (THC-COOH) were found in the postevent urine of 34% of LEOs. Neither ?9-THC nor its metabolites were detected in any blood sample. LEOs reported experiencing non-specific symptoms during the concerts, such as burning, itchy, or red eyes (31%); dry mouth (21%); headache (21%); and coughing (21%).


Identification of ?9-THC in the breathing zone for some LEOs indicates the potential for airborne exposure to the psychoactive component of cannabis. However, the magnitude of these exposures was small compared with those that would result in a dose of ?9-THC associated with psychotropic effects. Similarly, THC-COOH was found in the postevent urine of some LEOs at concentrations that were orders of magnitude below active use cut-points used during a cannabis screening test (50 ng ml-1). Exposure to SHCS was not high enough to detect concentrations of THC, THC-COOH, to OH-THC in the blood, which could be due to differences between the limits of detection for the tests employed. The ocular and respiratory symptoms reported by LEOs may be related to irritants in SHCS. However, the health effects of SHCS remain unclear, and further research concerning occupational and environmental exposures is warranted.

Authors: Wiegand DM, Methner MM, Grimes GR, Couch JR, Wang L, Zhang L, Blout BC
; Full Source: Annals of work exposures and health. 2020 Mar 27. pii: wxaa025. doi: 10.1093/annweh/wxaa025. [Epub ahead of print]